mt76: mt7915: make read-only array ppet16_ppet8_ru3_ru0 static const

Don't populate the read-only array ppet16_ppet8_ru3_ru0 on the stack but
instead make it static const. Also makes the object code a little smaller.
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7915/init.c

@@ -801,7 +801,7 @@ static void
 mt7915_gen_ppe_thresh(u8 *he_ppet, int nss)
 {
 	u8 i, ppet_bits, ppet_size, ru_bit_mask = 0x7; /* HE80 */
-	u8 ppet16_ppet8_ru3_ru0[] = {0x1c, 0xc7, 0x71};
+	static const u8 ppet16_ppet8_ru3_ru0[] = {0x1c, 0xc7, 0x71};
 
 	he_ppet[0] = FIELD_PREP(IEEE80211_PPE_THRES_NSS_MASK, nss - 1) |
 		     FIELD_PREP(IEEE80211_PPE_THRES_RU_INDEX_BITMASK_MASK,